Cards or labels are known by those skilled in the art where components are mounted on a substrate, on which conductive tracks and connection areas (usually in copper) are engraved. The components are usually bonded, then their contacts are welded onto the tracks or onto the conductive connection areas of the substrate. The electric contact between the connection areas of the component and those of the substrate is achieved by means such as: bonding with a conductive glue, welding by means of ultrasounds, welding by means of a hot applied tin-based alloy.
Cards are also known that are provided with components whose contacts are provided with claws or spikes (bumps) which are embedded by pressing into the engraved connection areas of the substrate. The document WO0055808 describes the production of a connection between a chip and the contact areas of an antenna by hot lamination. The contacts of the chip include bumps that are embedded in the conductive material of the antenna's connection area producing a deformation in these areas.
The connections of components on substrate conductors can also be obtained by means of conductive wires welded on one hand on a substrate conductor and on the other hand on a conductive area of the component.
In order to protect the components and the circuits wired in this way, an epoxy resin can be cast on all or part of the substrate surface in order to coat the circuit components assembly. According to another embodiment, an insulating sheet is laminated on all or part of the substrate that cons the component or components and the conductive tracks in the vicinity.
The document EP0786357 describes a contactless card that comprises a chip mounted on a substrate and connected to an antenna coil placed on the edge of the substrate. The chip is placed in a substrate zone located on the exterior of the loop formed by the antenna coil in the vicinity of one of the edges of the card. This off-center position of the chip protects the latter against stresses caused by bending of the card. The connection of the antenna coil to the chip is carried out by hot pressing the bumps of the chip contacts on the end tracks of the coil. According to a variant this connection is achieved by soldering of wires (“wire-bonding”) between the chip contacts and the tracks deriving from the coil.
The document US2002/0110955 describes a manufacturing method of an electronic module comprising a substrate and at least one chip. The latter is either glued on one of the substrate faces, or hot pressed inside the substrate thickness in order to be level with the surface. Furthermore, the substrate includes conductive areas to which the chip is connected by means of conductive tracks made by silk-screening, according to a preferred variant. The chip contacts include bumps on which tracks, thus applied, end up to con the bumps. A final step consists in applying a thin film or a protection lacquer on the chip and on the conductive tracks located near the chip.
The transponders whose components are assembled according to the known processes described above present a disadvantage at the level of quality and reliability of the connection between the component and conductors. In fact, this connection can be interrupted totally or intermittently due to mechanical stresses applied to the transponder during its use. More particularly, the thin transponders such as cards or electronic labels are easily deformable by flexion or twisting. These stresses can appear during the normal application of the transponder such as for example on a label that is applied on the surface of an object presenting protrusions.
Despite the protection of the components by coating or lamination of an insulating film, the connections of the components are subjected to internal traction and compression causing their breakage when the transponder is deformed. This phenomenon is further increased during repetitive deformations leading to the strain of the connection that will finally break after a few flexions or torsions suffered by the transponder.